Hydraulic machines

ABSTRACT

A hydraulic machine constructed and arranged to be driven and transmit fluid from a source of supply through a series of perforated pistons to a pressurized chamber provided adjacent to bearing means supporting a driving shaft.

limited States Patent 1191 Weigle 1 51 Apr. 17, 1973 1541 HYDRAULIC MACHINES 3,157,130 11/1964 Cadiou ..91/6.5 2,155,455 4/1939 Thoma... [75] Inventor. D1eter Wergle, Ulm/Danube, Ger- 2,850,986 9/l958 Grad n many 3,266,434 8/1966 NcAluoy....

3 396 670 8/1968 Baits ..91/506 73 A Sslgnee gonstamm Rauch Ulm/Danube 2,699,123 1/1955 Bonnette et al. ..91/488 many 3,198,131 8/1965 Thoma 22 i ()CL 1 1970 3,512,178 5/1970 Russell 3,173,376 3/1965 Hulmann et al. [21 Appl. No.: 81,457 2,129,828 9/1938 Dunn ..91/475 FOREIGN PATENTS OR APPLICATIONS [30] Foreign Application Priority Data 1,372,669 8/1964 France ..91/507 Oct. 17, 1969 Germany ..P 19 52 472.2

Primary Examiner-William L. Fresh [52] US. Cl ..91/505 Attorney-Edwin E. Greigg [51] Int. Cl ..F0lb 13/06 [58] Field of Search ..91/488, 504506 [57] ABSTRACT A hydraulic machine constructed and arranged to be [56] Reierences cued driven and transmit fluid from a source of supply UNITED STATES PATENTS through a series of perforated pistons to a pressurized chamber provided adjacent to bearingmeans support- 2,298,850 10/1942 Ullkers ..91/487 ing a driving h ft 2,852,320 9/1958 Cornelius ..91/507 3,159,041 12/1964 Firth et al ..91/506 9 Claims, 6 Drawing Figures j v \m 1 1 n 7 \L -m I w a 9 20 \18 J 19 J 1 s PATENTEDAPR 1 W5 :5, 727. 522

SHEET 1 OF 3 Fig. 2 Fig. 1

PATENTED APR 1 71975 SHEET 2 OF 3 Fig. 3

Fig. 4

PATENTEI] APR 1 7 I975 SHEET 3 [IF 3 Fig. 6

HYDRAULIC MACHINES The invention relates to hydraulic machines and is applicable to the mounting of the driving shaft of a pressurized fluid axial piston machine wherein the driving shaft and a driving disc form a rigid unit, which is supported by means of at least one bearing in a pivotally supported per se rigid bearing carrier, and is also supported in a further, spatially and constructionally separate bearing.

The life and loading capacity of such mountings depends on the rigidity of their construction, and also on the degree to which it is possible to compensate alignment errors in the mounting.

An axial piston machine of the above-mentioned kind has been proposed in which is provided a bearing carrier which comprises both a radial and an axial driving shaft bearing and is swingably mounted in the gear housing by means of its spherical carrying surface. Since the bearing carrier is a component of the swinging bearing of the axial piston machine, the swinging axis of the bearing carrier, for kinematic reasons, must be identical with the swinging axis of the axial piston machine, so that alignment errors occurring in the bearing sliding surfaces are not only not compensated for but are reinforced.

A device has been proposed in which the driving disc is yieldingly connected to the primary or secondary drive of the machine for compensating alignment errors. This construction implies a radial mounting of the driving disc on its external diameter, resulting in considerable constructional volume and high peripheral speeds in the bearing. Furthermore, the loading capacity of the machine is limited in that the full torque has to be transmitted by the yielding connecting element positioned between driving shaft and driving disc.

An axial piston machine of the first-mentioned kind can be constructed in which there is provided between the driving disc and pump housing a cardanically movable preferably spherical pendulum ring, on whose sliding surface the back of the driving disc is supported. This construction receives the axial bearing forces only centrally, so that considerable additional loads result from the eccentrically applied axial piston forces. Compensation of the alignment errors in the sliding surfaces of the radial bearing of the driving shaft is not possible by means of this arrangement. Furthermore, it is necessary to relieve the movable pendulum ring of the load on its housing side supporting surface by means of pressure fields, in order to keep down the frictional forces opposing the adjusting movements, whence, in addition to a substantial increase in manufacturing costs, there also results in a doubling of leakages.

In another axial piston machine of this kind an axial and a radial sliding bearing can be also arranged in a swingable bearing carrier. In this construction, there is no spatially and constructionally separate second radial bearing, which results in high loading of the existing bearings. In addition, for compensating alignment errors, the shaft end facing away from the driving disc must be freely movable.

It is consequently desirable to improve the mounting of the driving shaft of an axial piston machine using sliding bearings and a pivotally supported, per se rigid bearing carrier, by means of a simple and low-leakage construction, such that radial and/or axial bearing forces are avoided while any alignment errors in the radial and/or axial sliding surfaces of the bearings are minimized.

Accordingly, in one axial piston machine embodying the present invention, the bearing or bearings in the bearing carrier are constructed in the manner known per se as radial sliding bearings, and the bearing carrier is supported in the machine housing pivotally with respect to an axis which is parallel to the swinging axis (control axis) of the axial piston machine and which is situated in the direction of the further spatially separated bearing outside the central plane of the carrying part of the bearing length of the radial sliding bearing or bearings. Additionally, an axial sliding bearing may be provided in the bearing carrier.

With a bearing carrier of such construction, supported pivotally with respect to a definite axis, the alignment errors in all sliding surfaces can be compensated automatically, and nevertheless the eccentrically engaging axial piston forces can be absorbed without any reactions on the radial bearings.

In an embodiment of the invention of particularly simple construction, the bearing carrier is radially and swingably supported on the bearing housing by means of a spherically convex part, and rests axially on two supporting surfaces connected to the bearing housing, the centers of gravity of which supporting surfaces lie in the plane defined by the pump swinging axis and the driving shaft axis.

Advantageously, the axial bearing additionally provided in the bearing carrier can be constructed as a hydraulic pressure chamber bearing such that there is associated with each piston a pressure chamber which is supplied with throttled pressurized fluid from the corresponding cylinder by way of a duct in the piston and in the ball rod. The stationary surface of the axial sliding bearing which has two bores are connected together by a pressure transference duct that opens in the region of the pressure chambers, the bores being substantially diametrically opposed to one another with respect to the shaft axis and are spaced apart one from the other in a direction substantially perpendicular to the shaft axis and the swinging axis. By means of this arrangement, the pressure change in the pressure chambers is accelerated, and on the one hand, the load shocks occurring in the cylinder chambers on the change in pressure are gently absorbed in prepared pressure cushions, while, on the other hand, any forces rotating the bearing carrier, and hence torques impairing the alignment, are prevented.

The invention will be better understood, as well as further objects and advantages will become more apparent, from a reading of the following specification taken in conjunction with the drawings, in which:

FIG. 1 shows a longitudinal cross-sectional view through an axial piston machine embodying the invention;

FIG. 2 shows a longitudinal cross-sectional view according to FIG. 1 turned through FIG. 3 shows a longitudinal cross-sectional view through another embodiment;

FIG. 4 shows a longitudinal cross-sectional view according to FIG. 3 turned through 90;

FIG. 5 shows a diagrammatic and schematic representation of the geometrical relationship between a control surface of an axial piston machine embodying the invention and an axial bearing with a pressure duct of that machine; and

FIG. 6 shows a section in the circumferential direction through pressure chambers of an axial bearing for an axial piston machine embodying the present invention.

A motor, not shown, drives the axial piston pump 1, which is swingable about the axis [-1, by means of the driving shaft 2 having a flange means rigidly connected therewith and comprised by a driving disc 3, the driving disc 3 setting the cylinder drum 4 in rotation against the control surface 15 by means of the ball-headed piston rods 5 and the pistons 6. During a revolution of the cylinder drum 4, each piston 6 reciprocates in its cylinder bore 16, drawing oil through a suction element 17 and pumping it through a pressure element opposite the suction element 17 to a consumer, not shown.

The driving shaft-driving disc unit 2, 3 is carried by a bearing 28, axial-thrust bearing means in the. form of an axial sliding bearing 7, and sleeve bearing means constituted by a radial sliding bearing 8. The two sliding bearings 7 and 8 are fixed according to the invention on a common rigid bearing carrier 9, which by means of two trunnions 10 (one shown in dotted lines) is mounted in the machine housing 11 pivotally with respect to an axis II--II, parallel to the swinging axis I-- I of the pump and to the center plane III-IIIof the carrying part of the bearing length of the radial bearing 8. The eccentricity of the axis II-II relative to the central plane III-III is dimensioned such that the resultant radial bearing force applied to the center of the radial bearing 8 produces a torque about the axis II-II which cancels all the forces, for example, frictional forces, acting on it from the outside and impeding the adjusting movements of the bearing carrier 9. Thus, the bearing carrier 9 can follow any obliquity of the driving shaft-driving disc unit 2, 3, caused by transverse forces, without the bearing surfaces being loaded by additional forces producing the adjustment, and does not allow any alignment errors to occur in the sliding surfaces of the bearings 7 and 8.

Centering of the bearing disc 13 of the axial sliding bearing 7 makes it possible, on the one hand, to obtain by simple means exact geometrical coordination of the two journal bearings with each other, and on the other hand, provides the rigid bearing carrier 9 with a form which can be made accurately at low cost. Resilient means, for example springs 12, are arranged in the machined housing 11, such that they exert forces on the bearing body 9 which counteract its turning movement out of a central position, so that the bearing carrier 9 is set in its geometrically exact central position if the transverse forces, producing obliquity of the driving shaft 2, are eliminated.

In FIGS. 3and 4 there is illustrated a further, simplified embodiment of the swingable bearing of the bearing flange 9. In this embodiment the bearing flange 9 braces itself by means of the convex part 22 against the machine housing 11 in a radial and swingable manner, whereby the plane V-V assumes the functions of the swivel axis II-II (see FIGS. 1 and 2) and at the same time the bearing rests axially on two small supporting surfaces 23 which latter brace themselves directly or indirectly against the machine housing 11, as shown. The centers of gravity of the two narrow supporting surfaces 23 lie in a plane defined by the pump swinging axis II (FIGS. 1 and 2) and the driving shaft axis IV--IV shown in that view.

Each piston rod 5 further includes ball portions at its opposite ends with one being carried in the driving disc 3, while the other is positioned in the perforated piston 19. It is apparent from this that the cylinder bore 16 can, by reason of the channel 19, communicate with the pressure chamber 18. Throttles 20, which can be located in the driving flange 3 and/or in the piston 6, are responsible for a functionally measuring of the pressure fluid in the pressure chamber 18. Each axial bearing sector with its pressure chamber is shaped such that the force vector applied by it to the driving disc 3 has the same or approximately the same distance from the driving shaft axis IV-IV as the vector of the correspondingaxial piston force, both vectors being equal or approximately equal in magnitude. A definite part of the leakage of the pressure chamber bearing is led automatically by way of the annular chamber 21 or a duct into the radial sliding bearing 8 for its lubrication and cooling.

The form of pressure chambers 18 shown in FIG. 6 has proved particularly satisfactory; the side walls 25 terminate at an acute angle a on the sliding surface 27 of the bearing, thus ensuring by the combination of hydrostatic with hydrodynamic bearing effects the functioning and lubrication of the bearings under all working conditions, particularly in pressureless operation.

The pressure duct 24 shown in FIG. 5 connects, by means of the bores 26, oppositely situated pressure chambers 18 and thus takes on the function of accelerating the pressure change in the pressure chambers and thereby gently absorbing in prepared pressure cushions the load shocks occurring in the cylinder chambers 16 on a change in pressure. For this purpose, the bores 26 are arranged on the stationary surface of the axial bearing 7 such that they are covered by those pressure chambers 18 whose associated cylinder chambers 16 are situated adjacent to, or in the vicinity of, the reversing points of the axial piston machine at the control surface with respect to which the pistons and cylinders rotate.

That which is claimed is:

1. In a hydraulic machine comprising a plurality of parallel cylinders and pistons axially reciprocable therein, said cylinders and pistons being pivotal as a unit about a first pivot axis transverse to the longitudinal axes of the cylinders, a drive shaft parallel to the longitudinal axes of the cylinders, a drive disc rigidly attached to an end of said shaft and piston rods connecting the pistons and drive disc whereby rotation of the shaft causes the cylinders to rotate about the axis of the shaft and the pistons to reciprocate in the cylinders when the cylinders are pivoted about the said first axis so that their longitudinal axes are inclined to the shaft axis; the improvement comprising a bearing structure for said driving shaft which compensates for alignment errors, said bearing structure comprising a bearing carrier on which is mounted a plain radial sleeve bearing, and a radial bearing independent of said bearing carrier and spaced from said sleeve bearing in a direction away from said drive disc, said bearing carrier being pivotable relative to the machine housing about a second axis which is parallel to said first axis and on the opposite side of an axis in the median plane of the sleeve bearing mounted on said carrier and an axial thrust bearing for said drive disc also mounted on the bearing carrier, said sleeve bearing and said axial thrust bearing being rigidly related to each other and the carrier.

2. A machine as claimed in claim 1, in which resilient means act on said bearing carrier to center it.

3. A machine as claimed in claim 1, in which the bearing carrier has a convex surface contacting a surrounding housing so that it may pivot about said second axis and there are two support areas on the housing with which the bearing carrier has axial contact, the centers of gravity of said support areas lying in a plane defined by said first axis and the axis of said drive shaft.

4. A machine as claimed in claim 1, in which said axial thrust bearing surrounds an end of the radial sleeve bearing and is centered by it.

5. A machine as claimed in claim 1, in which said axial thrust bearing and said driving disc cooperate to form hydrostatic pressure chambers and at least a part of the leakage from said chambers is constrained to flow through the bearing area of said sleeve bearing.

6. A machine as claimed in claim 5, in which a separate duct connects two pressure chambers diametrically opposed with respect to the axis of said drive shaft.

7. A machine as claimed in claim 5, in which the pistons and piston rods are formed with ducts to supply fluid from said cylinders to said pressure chambers, the piston rods being connected to said driving disc by ball joints, said ducts passing through said ball joints and being connected to said pressure chambers by throttling restrictions.

8. A machine as claimed in claim 7, in which said pressure chambers are recessed into said driving disc and the walls of said chambers are at an acute angle with the overlying wall of the axial thrust bearing.

9. A machine as claimed in claim 8, in which a separate duct connects two pressure chambers diametrically opposed with respect to the axis of said drive shaft. 

1. In a hydraulic machine comprising a plurality of parallel cylinders and pistons axially reciprocable therein, said cylinders and pistons being pivotal as a unit about a first pivot axis transverse to the longitudinal axes of the cylinders, a drive shaft parallel to the longitudinal axes of the cylinders, a drive disc rigidly attached to an end of said shaft and piston rods connecting the pistons and drive disc whereby rotation of the shaft causes the cylinders to rotate about the axis of the shaft and the pistons to reciprocate in the cylinders when the cylinders are pivoted about the said first axis so that their longitudinal axes are inclined to the shaft axis; the improvement comprising a bearing structure for said driving shaft which compensates for alignment errors, said bearing structure comprising a bearing carrier on which is mounted a plain radial sleeve bearing, and a radial bearing independent of said bearing carrier and spaced from said sleeve bearing in a direction away from said drive disc, said bearing carrier being pivotable relative to the machine housing about a second axis which is parallel to said first axis and on the opposite side of an axis in the median plane of the sleeve bearing mounted on said carrier and an axial thrust bearing for said drive disc also mounted on the bearing carrier, said sleeve bearing and said axial thrust bearing being rigidly related to each other and the carrier.
 2. A machine as claimed in claim 1, in which resilient means act on said bearing carrier to center it.
 3. A machine as claimed in claim 1, in which the bearing carrier has a convex surface contacting a surrounding housing so that it may pivot about said second axis and there are two support areas on the housing with which the bearing carrier has axial contact, the centers of gravity of said support areas lying in a plane defined by said first axis and the axis of said drive shaft.
 4. A machine as claimed in claim 1, in which said axial thrust bearing surrounds an end of the radial sleeve bearing and is centered by it.
 5. A machine as claimed in claim 1, in which said axial thrust bearing and said driving disc cooperate to form hydrostatic pressure chambers and at least a part of the leakage from said chambers is constrained to flow through the bearing area of said sleeve bearing.
 6. A machine as claimed in claim 5, in which a separate duct connects two pressure chambers diametrically opposed with respect to the axis of said drive shaft.
 7. A machine as claimed in claim 5, in which the pisTons and piston rods are formed with ducts to supply fluid from said cylinders to said pressure chambers, the piston rods being connected to said driving disc by ball joints, said ducts passing through said ball joints and being connected to said pressure chambers by throttling restrictions.
 8. A machine as claimed in claim 7, in which said pressure chambers are recessed into said driving disc and the walls of said chambers are at an acute angle with the overlying wall of the axial thrust bearing.
 9. A machine as claimed in claim 8, in which a separate duct connects two pressure chambers diametrically opposed with respect to the axis of said drive shaft. 